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cifs: Fix preauth hash corruption

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smb311_update_preauth_hash() uses the shash in server->secmech without
appropriate locking, and this can lead to sessions corrupting each
other's preauth hashes.

The following script can easily trigger the problem:

	#!/bin/sh -e

	NMOUNTS=10
	for i in $(seq $NMOUNTS);
		mkdir -p /tmp/mnt$i
		umount /tmp/mnt$i 2>/dev/null || :
	done
	while :; do
		for i in $(seq $NMOUNTS); do
			mount -t cifs //192.168.0.1/test /tmp/mnt$i -o ... &
		done
		wait
		for i in $(seq $NMOUNTS); do
			umount /tmp/mnt$i
		done
	done

Usually within seconds this leads to one or more of the mounts failing
with the following errors, and a "Bad SMB2 signature for message" is
seen in the server logs:

 CIFS: VFS: \\192.168.0.1 failed to connect to IPC (rc=-13)
 CIFS: VFS: cifs_mount failed w/return code = -13

Fix it by holding the server mutex just like in the other places where
the shashes are used.

Fixes: 8bd68c6e47abff34e4 ("CIFS: implement v3.11 preauth integrity")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
CC: <stable@vger.kernel.org>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Vincent Whitchurch 2021-03-10 13:20:40 +01:00 committed by Steve French
parent 5171317dfd
commit 05946d4b7a
1 changed files with 6 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/cifs/transport.c
View File

@ -1196,9 +1196,12 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
/*
* Compounding is never used during session establish.
*/
if ((ses->status == CifsNew) || (optype & CIFS_NEG_OP) || (optype & CIFS_SESS_OP))
if ((ses->status == CifsNew) || (optype & CIFS_NEG_OP) || (optype & CIFS_SESS_OP)) {
mutex_lock(&server->srv_mutex);
smb311_update_preauth_hash(ses, rqst[0].rq_iov,
rqst[0].rq_nvec);
mutex_unlock(&server->srv_mutex);
}
for (i = 0; i < num_rqst; i++) {
rc = wait_for_response(server, midQ[i]);
@ -1266,7 +1269,9 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
.iov_base = resp_iov[0].iov_base,
.iov_len = resp_iov[0].iov_len
};
mutex_lock(&server->srv_mutex);
smb311_update_preauth_hash(ses, &iov, 1);
mutex_unlock(&server->srv_mutex);
}
out: